1. Field of the Invention
The present invention relates to a catalyst composition for transalkylation of alkylaromatic hydrocarbons and to a process for production of xylene. More particularly, the present invention relates to a catalyst composition for production of xylene from a feedstock containing C.sub.9 alkylaromatic hydrocarbons by transalkylation and to a process for production of xylene.
2. Description of the Prior Art
Transalkylation of alkylaromatic hydrocarbons is one of the industrially important reactions which is applied to the production of benzene and xylene from toluene by disproportionation and the production of xylene from toluene and methylbenzene by transalkylation. There have been proposed a number of catalyst systems for this reaction. Among them is crystalline aluminosilicate zeolite (such as faujasite and mordenite) which is known as an effective catalyst. Mordenite is particularly active in transalkylation of alkylaromatic hydrocarbons.
Unfortunately, mordenite used alone is not satisfactory in activity and catalyst life; therefore, it is used in combination with a metal from Group VIB (such as chromium, molybdenum, and tungsten) or a metal from Group VIII (such as iron, cobalt, nickel, and platinum metal), as disclosed in U.S. Pat. No. 3,729,521. In addition, there is disclosed a catalyst which substantially consists only of mordenite and rhenium, in Japanese Patent Publication No. 45849/1987. These catalysts, however, are not wholly effective for transalkylation in production of xylene from C.sub.9 alkylaromatic hydrocarbons (including ethyltoluene). Incidentally, J. Das et al. reported transalkylation of feedstocks containing C.sub.9 alkylaromatic hydrocarbons by .beta.-zeolite (Catalysis Letters, vol. 23 (1994), p. 161-168). In actuality, this process is not satisfactory in xylene yields. Practically, there exists no efficient way of producing xylene from C.sub.9 alkylaromatic hydrocarbons containing ethyltoluene.